   + t w2 (t w1 - t w2) . It is straightforward to see that by choosing \(\rho _2 = 0, \mathbf {u}_2 = 0, w_2 = 0\) , the relative energy inequality reduces to the energy inequality \((\ref {energy})\) . Also, if one chooses \(w_1 = w_2 = 0\) , then relative entropy and relative energy inequality take the form of the ones defined in [1]}.
